Mmmm unfortunatly you are not going to be able to diagnose this very easily at all. At a guess i would say it a faulty CIM (central intelegence module) do all the other stalk functions work and do the radio and horn buttons work on the steering wheel? These also work via the CIM. Speak nicely to your vaxhall dealer and ask them to check it out with tech 2.
Sarah Jack
January 2010